Contemporary telecommunication systems often employ a variety of network layer protocols, physical interfaces, and physical transmission mediums to facilitate communication between remotely located telecommunication network stations. The transmission and management of these multi-protocol signals is traditionally facilitated by the multiplexing of electronic signals into standard digital hierarchies such as the North American Hierarchy (DS1, DS1C, DS2 and DS3) as well as E-1 (European standard) and ATM, or in LAN environments Token Ring, Ethernet and FDDI (Fiber Distributed Data Interface) formats. However, as telecommunication system operators seek reduction in system costs and increased system performance, telecommunication protocols utilizing high bandwidth digital multiplexing formats for the transmission of data are increasingly preferred.
High bandwidth multiplexing protocols such as SONET, Synchronous Optical Network, and SDH, Synchronous Digital Hierarchy, multiplex and transmit tributary signals across a synchronous network via high bandwidth physical media. SONET and SDH employ their own unique digital multiplexing hierarchy which support various communication rates for the transport of multiplexed payloads.
For example, the SONET hierarchy is based on a modular signal, referred to as STS-1,having a 51.840 Mbps communication rate. A tributary signal such as DS3 with a line rate of 44.736 Mbps is assembled into a synchronous signal envelope (STS-1 format) by a process known as payload mapping. The essence of the mapping process is to synchronize the tributary signal with the envelope capacity provided for transport. This is achieved by adding extra stuffing bits (also called justification bits) to the STS-1 signal bit stream as part of the mapping process. For example, a DS3 tributary signal at a nominal rate of 44 Mbps needs to be synchronized with an envelope capacity of 51.840 Mbps (minus STS path overhead). In such manner an, asynchronous low bandwidth payload is embedded within a high bandwidth multiplexed synchronous signal.
The low bandwidth asynchronous payloads are usually processed according to a desired signal processing algorithm for facilitating such functions as data compression, echo cancellation, error correction coding, and voice and data encryption/decryption. Before the present invention was made, it was not easy to reliably retrieve the asynchronous timing relationships between individual payloads subsequent to the signal processing function.
The system in accordance with the present invention processes the asynchronous payloads embedded within synchronous signal envelopes by such communication protocols as SONET and SDH. The retention of timing relationships is maintained by de-multiplexing the asynchronous payloads, synchronizing the asynchronous payloads for processing, processing the asynchronous payloads according to a desired signal conditioning algorithm, and then reassembling the asynchronous payloads to their original embedded format with the original timing relationships.